1. Field of the Invention
The present invention relates to techniques for determining fluid parameters. More particularly, the present invention relates to techniques for determining electrical parameters of downhole fluids.
2. Background of the Related Art
Oil rigs are positioned at wellsites for performing a variety of oilfield operations, such as drilling a wellbore, performing downhole testing and producing located hydrocarbons. Downhole drilling tools are advanced into the earth from a surface rig to form a wellbore. Drilling muds are often pumped into the wellbore as the drilling tool advances into the earth. The drilling muds may be used, for example, to remove cuttings, to cool a drill bit at the end of the drilling tool and/or to provide a protective lining along a wall of the wellbore. During or after drilling, casing is typically cemented into place to line at least a portion of the wellbore. Once the wellbore is formed, production tools may be positioned about the wellbore to draw fluids to the surface.
During drilling, measurements are often taken to determine downhole conditions. In some cases, the drilling tool may be removed so that a wireline testing tool may be lowered into the wellbore to take additional measurements and/or to sample downhole fluids. Once the drilling operation is complete, production equipment may be lowered into the wellbore to assist in drawing the hydrocarbons from a subsurface reservoir to the surface.
The downhole measurements taken by the drilling, testing, production and/or other wellsite tools may be used to determine downhole conditions and/or to assist in locating subsurface reservoirs containing valuable hydrocarbons. Such wellsite tools may be used to measure downhole parameters, such as temperature, pressure, viscosity, resistivity, etc. Such measurements may be useful in directing the oilfield operations and/or for analyzing downhole conditions.
In particular, it is often desirable to determine what types of fluids are present in the wellbore. Various techniques have been developed for measuring wellbore fluids as described, for example, in US Patent/Application No. 20090204346. Techniques have also been developed for using electrodes in downhole tools as described, for example, in US Patent/Application No. 20090090176 and 6801039. In some cases, electrodes have been used for measuring fluid properties as described, for example, in US Patent/Application Nos. 20090153155, 7258005, 5457396, 6527923, and 4608983.
Despite the development of techniques for measuring wellbore fluids and/or in the use of electrodes, there remains a need to provide advanced techniques for determining parameters of wellbore fluids using wellsite tools. It may be desirable to provide techniques that enhance downhole fluid measurements. It may be further desirable to provide techniques that reduce the effects of other components, such as conductive components, that may interfere with measurements. Preferably, such techniques involve one or more of the following, among others: accuracy of measurements, optimized measurement processes, reduced clogging, minimized components, reduced size, increased surface area for measurement, constant flow of fluids during measurement, optimized shape of measurement apparatus/system, real time capabilities, compatibility with existing wellsite equipment, operability in downhole conditions (e.g., at high temperatures and/or pressures), etc.